A multiple ratio automotive vehicle transaxle of known design, such as the transaxle disclosed in U.S. Pat. No. 4,509,389, comprises a hydrokinetic torque converter and multiple ratio gearing for establishing multiple torque ratio torque flow paths between an engine and axle half shaft of the kind found, for example, in front-wheel drive vehicle powerstrains. The torque converter has a bladed impeller driven by the engine and a bladed turbine adapted to be clutched to torque input elements of the gearing. Such transaxle include fluid pressure operated clutch and blade servos for controlling relative motion of planetary gear elements in the transaxle gearing to establish the multiple torque ratio flow paths. The clutch and brake servos form a part of a hydraulic valve system. Examples of such systems are shown in U.S. Pat. Nos. 4,633,738 and 4,665,770.
Such systems normally include mechanical throttle valve systems that are actuated by engine carburetor throttle controls or engine manifold pressure responsive actuators. They include also timing orifices, separate regulators for regulating, for example, supply pressure for clutch servos and shift inhibitors so that the necessary shift strategy for optimum performance is achieved hydraulically.
The control system of the '738 patent includes a torque converter clutch for establishing a lock-up condition to effect a direct drive from the engine to the converter turbine. The converter clutch, in turn, is controlled by a bypass clutch solenoid valve.
The valve system of the '738 patent, like other known prior art valve systems for multiple ratio transmissions, includes a mechanical governor assembly for developing a signal that is representative of vehicle speed.